A directory-category for terminal emulators

This is a mostly cosmetical commit, in the sense it doesn't change the contents
of any package, but reorganizes the overall Nixpkgs expressions.

Terminal emulators are an ubiquitous tool for any Unix user; even the beginners
are routinely familiarized to it. And, manifestly, there are many
implementations of terminal emulators out there, from those traditionally made
in C and C++ to those written in Haskell and Go.

Terminal emulators deserve more highlight. This commit does that by creating a
category for them.

pkgs/applications/terminal-emulators/stupidterm/default.nix

@@ -0,0 +1,36 @@
+{ stdenv, fetchFromGitHub, pkgconfig, vte, gtk, pcre2 }:
+
+stdenv.mkDerivation {
+  pname = "stupidterm";
+  version = "2019-03-26";
+
+  nativeBuildInputs = [ pkgconfig ];
+
+  buildInputs = [ vte gtk pcre2 ];
+
+  src = fetchFromGitHub {
+    owner = "esmil";
+    repo = "stupidterm";
+    rev = "f824e41c2ca9016db73556c5d2f5a2861e235c8e";
+    sha256 = "1f73wvqqvj5pr3fvb7jjc4bi1iwgkkknz24k8n69mdb75jnfjipp";
+  };
+
+  makeFlags = [ "PKGCONFIG=${pkgconfig}/bin/${pkgconfig.targetPrefix}pkg-config" "binary=stupidterm" ];
+
+  installPhase = ''
+    install -D stupidterm $out/bin/stupidterm
+    install -D -m 644 stupidterm.desktop $out/share/applications/stupidterm.desktop
+    install -D -m 644 stupidterm.ini $out/share/stupidterm/stupidterm.ini
+
+    substituteInPlace $out/share/applications/stupidterm.desktop \
+      --replace "Exec=st" "Exec=$out/bin/stupidterm"
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Simple wrapper around the VTE terminal emulator widget for GTK";
+    homepage = "https://github.com/esmil/stupidterm";
+    license = licenses.lgpl3Plus;
+    maintainers = [ maintainers.etu ];
+    platforms = platforms.linux;
+  };
+}